TW201532086A - Rare earth permanent magnet and production method for rare earth permanent magnet - Google Patents

Abstract

The present invention provides a rare earth permanent magnet whose density is increased after sintering, and a method for producing a rare earth permanent magnet. A compound (12) is formed by grinding a magnet raw material into a magnet powder and mixing the ground magnet powder with an adhesive. Then, the compound (12) is molded into a sheet on a supporting base (13) by hot melt molding, thereby producing a raw sheet (14). After that, the molded raw sheet (14) is heated and softened, and magnetic field orientation is carried out by applying a magnetic field to the heated raw sheet (14). The raw sheet (14) after the magnetic field orientation is sintered in vacuum, and is subsequently sintered under pressure, thereby producing a permanent magnet (1).

Description

Method for manufacturing rare earth permanent magnet and rare earth permanent magnet

The invention relates to a method for manufacturing a rare earth permanent magnet and a rare earth permanent magnet.

In recent years, permanent magnet motors used in hybrid electric vehicles, hard disk drives, and the like have been required to be small, lightweight, high in output, and high in efficiency. Therefore, when the permanent magnet motor is reduced in size, weight, output, and efficiency, it is required to further improve the thickness and magnetic properties of the permanent magnet embedded in the motor.

Here, as a method of manufacturing a permanent magnet used in a permanent magnet motor, a powder sintering method has been conventionally used. Here, the powder sintering method firstly produces a magnet powder obtained by pulverizing a raw material by a jet mill (dry pulverization) or the like. Thereafter, the magnet powder is placed in a mold and press-formed into a desired shape. Then, the solid magnet powder formed into a desired shape is sintered at a specific temperature (for example, 1100 ° C when it is a Nd—Fe—B-based magnet), thereby producing a permanent magnet (for example, Japanese Patent Laid-Open No. 2) -266503). Further, in general, for permanent magnets, in order to improve magnetic characteristics, magnetic field alignment is performed by applying a magnetic field from the outside. Further, in the conventional method for producing a permanent magnet by a powder sintering method, a magnet powder is filled into a mold at the time of press molding, and a magnetic field is applied to perform magnetic field alignment, and then a pressure is applied to form a compacted body. Further, other methods for producing permanent magnets such as an extrusion molding method, an injection molding method, and a calender molding method apply pressure to an environment in which a magnetic field is applied to form a magnet. Thereby, it is possible to form a molded body in which the direction of the easy magnetization axis of each of the magnet particles constituting the permanent magnet coincides with the direction in which the magnetic field is applied.

[Previous Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open No. Hei 2-266503 (page 5)

Here, as one of the causes of lowering the magnetic properties of the magnet, a void is formed inside the magnet. Therefore, in order to eliminate these voids, it is important to increase the density (total densification) of the magnet after sintering. However, in the prior sintering method, the density of the magnet after sintering has not been sufficiently increased.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a method for producing a rare earth permanent magnet and a rare earth permanent magnet which is sintered by non-pressure sintering. Further, sintering is performed by pressure sintering, whereby the density of the permanent magnet after sintering is increased, and the magnetic properties of the permanent magnet are improved.

In order to achieve the above object, the rare earth permanent magnet of the present invention is characterized by the steps of: pulverizing a magnet raw material into a magnet powder; and forming a shaped body by molding the pulverized magnet powder; a step of performing magnetic field alignment by applying a magnetic field to the molded body; a step of sintering the formed body aligned by a magnetic field by non-pressure sintering; and a pressurization by a vertical direction with respect to a direction in which a magnetic field is applied Press-sintering is a step of sintering the sintered body which is sintered as described above by the non-pressure sintering.

Further, the rare earth permanent magnet of the present invention is characterized in that it is a rare earth permanent magnet of the first aspect, and is subjected to uniaxial pressure sintering in the step of sintering the sintered body by pressure sintering. sintering.

Further, the rare earth permanent magnet of the present invention is characterized in that it is burned by pressure as described above. In the step of sintering the sintered body, sintering is performed by electric conduction sintering.

Further, the rare earth permanent magnet of the present invention is characterized in that the density of the rare earth permanent magnet obtained by sintering by pressure sintering is 95% or more.

Further, the rare earth permanent magnet of the present invention is characterized in that the molded body is calcined in a non-oxidizing atmosphere before the non-pressure sintering of the formed body, thereby removing carbon in the molded body.

Further, the rare earth permanent magnet of the present invention is characterized in that, in the step of calcining the formed body, the formed body is heated to a set temperature in a non-oxidizing atmosphere at a temperature increase rate of 2 ° C/min or less. Maintain a certain time at the above set temperature.

Further, the rare earth permanent magnet of the present invention is characterized in that in the step of molding the magnet powder into a molded body, a mixture in which the magnet powder and the binder are mixed is produced, and the mixture is formed into a sheet shape to be produced. A green sheet of the above shaped body.

Further, in the rare earth permanent magnet of the present invention, in the step of molding the magnet powder into a molded body, the magnet powder is molded into the molded body by powder molding.

Further, the method for producing a rare earth permanent magnet of the present invention is characterized by comprising the steps of: pulverizing a magnet raw material into a magnet powder; forming a shaped body by molding the pulverized magnet powder; a step of applying a magnetic field to perform magnetic field alignment; a step of sintering the formed body aligned by a magnetic field by non-pressure sintering; and a pressure sintering by pressurizing in a direction perpendicular to a direction in which the magnetic field is applied The sintered body which is sintered by the above-described non-pressure sintering is further subjected to sintering.

Moreover, the method for producing a rare earth permanent magnet according to the present invention is characterized in that sintering is performed by uniaxial pressure sintering in the step of sintering the sintered body by pressure sintering.

Moreover, the method for producing a rare earth permanent magnet of the present invention is characterized in that In the step of sintering the sintered body by pressure sintering, sintering is performed by electric conduction sintering.

Moreover, the method for producing a rare earth permanent magnet according to the present invention is characterized in that the density of the rare earth permanent magnet obtained by sintering by pressure sintering is 95% or more.

Moreover, the method for producing a rare earth permanent magnet according to the present invention is characterized in that before the non-pressure sintering of the formed body, the formed body is calcined in a non-oxidizing atmosphere to remove the molded body. carbon.

Further, in the method for producing a rare earth permanent magnet according to the present invention, in the step of calcining the formed body, the molded body is heated to a temperature setting rate of 2 ° C/min or less in a non-oxidizing atmosphere. After the temperature, it is kept at the above set temperature for a certain period of time.

Further, in the method for producing a rare earth permanent magnet according to the present invention, in the step of molding the magnet powder into a molded body, a mixture in which the magnet powder and the binder are mixed is produced, and the mixture is formed into a sheet shape. A green sheet as the above molded body was produced.

Further, in the method for producing a rare earth permanent magnet according to the present invention, in the step of molding the magnet powder into a molded body, the magnet powder is molded into the molded body by powder molding.

According to the rare earth permanent magnet of the present invention having the above-described configuration, the molded body is sintered by non-pressure sintering, and then sintered by pressure sintering, whereby the density of the permanent magnet after sintering can be increased. Fully densified). Further, when the pressure sintering is performed, the sintered body is pressurized in the direction perpendicular to the direction in which the magnetic field is applied, so that the C axis of the magnet particles after the alignment is not pressed by the sintered body (the easy magnetization axis) ) The direction changes. Therefore, it is possible to prevent a decrease in magnetic properties without lowering the alignment degree.

Further, according to the rare earth permanent magnet of the present invention, in the step of sintering the sintered body by pressure sintering, sintering is performed by uniaxial pressure sintering, and thus is caused by sintering. The shrinkage becomes uniform, and deformation such as warpage or depression after sintering can be prevented. Moreover, it is also possible to prevent a decrease in the degree of alignment.

Further, according to the rare earth permanent magnet of the present invention, in the step of sintering the sintered body by pressure sintering, sintering is performed by electric conduction sintering, so that the temperature can be rapidly increased and cooled, and the temperature can be lowered in a lower temperature region. sintering. As a result, the temperature rise and the holding time in the sintering step can be shortened, and a dense sintered body which suppresses grain growth of the magnet particles can be produced.

Further, according to the rare earth permanent magnet of the present invention, by setting the density of the rare earth permanent magnet to 95% or more, it is possible to prevent the magnetic properties from being greatly lowered by the voids without forming voids inside the magnet.

Further, according to the rare earth permanent magnet of the present invention, even when the molded body is subjected to calcination treatment for decarburization, the density of the permanent magnet after sintering can be increased.

Further, according to the rare earth permanent magnet of the present invention, the molded body is heated to a set temperature at a temperature increase rate of 2 ° C/min or less in a non-oxidizing atmosphere, and then maintained at a set temperature for a predetermined period of time to be calcined. Therefore, the carbon contained in the formed body can be removed stepwise with a slow temperature change. Therefore, a rare earth permanent magnet having a high density can be produced without forming a large number of voids inside the magnet.

Further, according to the rare earth permanent magnet of the present invention, the magnet obtained by sintering the green sheet formed by mixing the magnet powder and the binder constitutes a permanent magnet, so that shrinkage due to sintering becomes uniform without sintering. After the deformation such as warping or depression, and the pressure unevenness in the case of no pressurization, the correction processing after the previous sintering is not required, and the manufacturing steps can be simplified. Thereby, the permanent magnet can be formed with higher dimensional accuracy.

Further, according to the rare earth permanent magnet of the present invention, even when the magnet powder is molded by powder compaction, the density of the permanent magnet after sintering can be increased.

Moreover, the method for producing a rare earth permanent magnet according to the present invention is produced by non-pressure burning After the cemented body is sintered and further sintered by pressure sintering, the density of the permanent magnet after sintering can be made higher (all densification). Further, when the pressure sintering is performed, the sintered body is pressurized in the direction perpendicular to the direction in which the magnetic field is applied, so that the C axis of the magnet particles after the alignment is not pressed by the sintered body (the easy magnetization axis) ) The direction changes. Therefore, it is possible to prevent a decrease in magnetic properties without lowering the alignment degree.

Further, according to the method for producing a rare earth permanent magnet of the present invention, in the step of sintering the sintered body by pressure sintering, sintering is performed by uniaxial pressure sintering, so that shrinkage due to sintering becomes uniform. It can prevent deformation such as warpage or depression after sintering. Moreover, it is also possible to prevent a decrease in the degree of alignment.

Further, according to the method for producing a rare earth permanent magnet of the present invention, in the step of sintering the sintered body by pressure sintering, sintering is performed by electric conduction sintering, so that the temperature can be rapidly increased and cooled, and the lower portion can be cooled. Sintering takes place in the temperature zone. As a result, the temperature rise and the holding time in the sintering step can be shortened, and a dense sintered body which suppresses grain growth of the magnet particles can be produced.

Moreover, according to the method for producing a rare earth permanent magnet of the present invention, by setting the density of the rare earth permanent magnet to be produced to 95% or more, it is possible to prevent the magnetic properties from being greatly lowered by the voids without forming voids in the magnet.

Moreover, according to the method for producing a rare earth permanent magnet of the present invention, even when the molded body is subjected to calcination treatment for decarburization, the density of the permanent magnet after sintering can be increased.

Further, according to the method for producing a rare earth permanent magnet of the present invention, the molded body is heated to a set temperature at a temperature increase rate of 2 ° C/min or less in a non-oxidizing atmosphere, and then held at a set temperature for a predetermined period of time. The calcination treatment can remove the carbon contained in the formed body stepwise with a slow temperature change. Therefore, a rare earth permanent magnet having a high density can be produced without forming a large number of voids inside the magnet.

Further, according to the method for producing a rare earth permanent magnet according to the present invention, by using a magnet The magnet obtained by sintering the green sheet formed by mixing the powder and the binder constitutes a permanent magnet, so that the shrinkage due to sintering becomes uniform without deformation such as warpage or depression after sintering, and no pressure is applied. The pressure is uneven, so the correction processing after the previous sintering is not required, and the manufacturing steps can be simplified. Thereby, the permanent magnet can be formed with higher dimensional accuracy.

Further, according to the method for producing a rare earth permanent magnet of the present invention, even when the magnet powder is molded by powder molding, the density of the permanent magnet after sintering can be increased.

1‧‧‧ permanent magnet

10‧‧‧ coarsely crushed magnet powder

11‧‧‧jet mill

12‧‧‧Complex

13‧‧‧Support substrate

14‧‧‧Life

15‧‧‧Mold

16‧‧‧ Block

17‧‧‧ Block

18‧‧‧ slit

19‧‧‧ cavity

20‧‧‧ supply port

21‧‧‧Spray outlet

22‧‧‧Application roller

25‧‧‧ Solenoid

26‧‧‧heating plate

27‧‧‧ arrow

30‧‧‧Magnetic field application device

31‧‧‧ coil department

32‧‧‧ coil part

33‧‧‧Magnetic pole pieces

34‧‧‧Magnetic pole pieces

35‧‧‧film

37‧‧‧ heating device

38‧‧‧Table components

39‧‧‧ hollow

40‧‧‧Formed body

41‧‧‧Sintering mould

42‧‧‧vacuum chamber

43‧‧‧Upper punch

44‧‧‧lower punch

45‧‧‧Upper punch electrode

46‧‧‧ Lower punch electrode

50‧‧‧Sintered body

D‧‧‧ gap

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a general view showing a permanent magnet of the present invention.

Fig. 2 is an explanatory view showing a manufacturing step of the permanent magnet of the present invention.

Fig. 3 is an explanatory view showing a step of forming a green sheet, particularly a green sheet, in the manufacturing process of the permanent magnet of the present invention.

Fig. 4 is an explanatory view showing a heating step and a magnetic field alignment step of a green sheet in the manufacturing process of the permanent magnet of the present invention.

Fig. 5 is a view showing an example in which a magnetic field is aligned in the vertical direction in the plane of the green sheet.

Fig. 6 is a view for explaining a heating device using a heat medium (polyoxygenated oil).

Fig. 7 is a view for explaining a heating state of a permanent magnet in the manufacturing process of the present invention, in particular, a calcination step.

Fig. 8 is an explanatory view showing a step of press-sintering of a sintered body in the manufacturing process of the permanent magnet of the present invention.

Fig. 9 is a view showing various measurement results of the respective magnets of the examples and the comparative examples.

Hereinafter, the method for producing the rare earth permanent magnet and the rare earth permanent magnet of the present invention will be described in detail with reference to the following embodiment.

[Composition of permanent magnets]

First, the configuration of the permanent magnet 1 of the present invention will be described. Figure 1 is a general view showing a permanent magnet 1 of the present invention. Further, the permanent magnet 1 shown in Fig. 1 has a fan shape, and the shape of the permanent magnet 1 changes depending on the punched shape.

The permanent magnet 1 of the present invention is an anisotropic magnet of the Nd-Fe-B system. Further, the content of each component is Nd: 27 to 40% by weight, B: 0.8 to 2% by weight, and Fe (electrolytic iron): 60 to 70% by weight. Further, in order to improve the magnetic properties, a small amount of Dy, Tb, Co, Cu, Al, Si, Ga, Nb, V, Pr, Mo, Zr, Ta, Ti, W, Ag, Bi, Zn, Mg, etc. may be contained. element. Fig. 1 is a view showing the entire permanent magnet 1 of the present embodiment.

Here, the permanent magnet 1 is a film-shaped permanent magnet having a thickness of, for example, 0.05 mm to 10 mm (for example, 1 mm). The permanent magnet 1 is produced by sintering a molded body formed by powder molding or a molded body (green body) obtained by mixing a mixture of a magnet powder and a binder as described below. Further, the green body is produced by molding a mixture (slurry or composite) in which a mixture of a magnet powder and a binder is mixed into a specific shape (for example, a sheet shape, a block shape, a final product shape, etc.) as follows. Further, the mixture may be temporarily molded into a shape other than the shape of the final product, and then subjected to punching, cutting, deformation processing, or the like, thereby forming a shape of the final product. Further, in particular, when the mixture is formed into a sheet shape and then processed into a final product shape, productivity can be improved by production in a continuous step, and the precision of molding can be improved. When the mixture is formed into a sheet shape, a film member having a film thickness of, for example, 0.05 mm to 10 mm (for example, 1 mm) is formed. Further, even in the case of forming a sheet shape, a large permanent magnet 1 can be produced by laminating a plurality of sheets.

Further, in the present invention, in particular, when the permanent magnet 1 is produced by sintering the green body, the binder mixed in the magnet powder may be a resin, a long-chain hydrocarbon, a fatty acid ester or a mixture thereof. .

Further, in the case where the binder is used as a binder, it is preferred that the structure does not contain oxygen. A polymer having an atom and having a depolymerization property. Further, as described below, the magnetic field alignment is performed in order to re-use the residue of the mixture produced by molding the mixture of the magnet powder and the binder into the final product shape, and in order to soften the formed mixture by heating it. And use a thermoplastic resin. Specifically, a polymer containing one or two or more polymers or copolymers selected from the monomers represented by the following formula (1) is suitable.

(wherein R ₁ and R ₂ represent a hydrogen atom, a lower alkyl group, a phenyl group or a vinyl group)

Examples of the polymer satisfying the above conditions include polyisobutylene (PIB) which is a polymer of isobutylene, polyisoprene (isoprene rubber, IR) which is a polymer of isoprene, and 1, Polybutadiene (butadiene rubber, BR) of 3-butadiene polymer, polystyrene as polymer of styrene, styrene-isoprene as copolymer of styrene and isoprene Diene block copolymer (SIS), butyl rubber (IIR) as a copolymer of isobutylene and isoprene, styrene-butadiene block copolymer as a copolymer of styrene and butadiene ( SBS), 2-methyl-1-pentene polymer resin as a polymer of 2-methyl-1-pentene, 2-methyl-1- as a polymer of 2-methyl-1-butene Butylene polymer resin, α-methylstyrene polymer resin as a polymer of α-methylstyrene, and the like. Further, in order to impart flexibility to the α-methylstyrene polymer resin, it is preferred to add a low molecular weight polyisobutylene. Further, the resin used as the binder may be a polymer or a copolymer (for example, polybutyl methacrylate or polymethyl methacrylate) containing a small amount of a monomer containing an oxygen atom. Further, a monomer which does not belong to the above formula (1) may be partially copolymerized. Even in this case, the object of the invention can be achieved.

Further, as the resin used in the binder, in order to appropriately perform the magnetic field alignment, it is preferably a thermoplastic resin which is softened at 250 ° C or lower, more specifically, a glass transition point or a thermoplastic resin having a melting point of 250 ° C or lower.

On the other hand, in the case where a long-chain hydrocarbon is used as the binder, it is preferred to use a long-chain saturated hydrocarbon (long-chain alkane) which is solid at room temperature and liquid at room temperature or higher. Specifically, it is preferred to use a long-chain saturated hydrocarbon having a carbon number of 18 or more. Further, when the mixture of the magnet powder and the binder is subjected to magnetic field alignment as described below, the mixture is heated in a state where the mixture is heated at a temperature higher than the melting point of the long-chain hydrocarbon to soften the magnetic field.

Further, when a fatty acid ester is used as the binder, it is also preferred to use methyl stearate or methyl behenate which is solid at room temperature and liquid at room temperature or higher. Further, when the mixture of the magnet powder and the binder is subjected to magnetic field alignment as described below, the magnetic field alignment is performed in a state where the mixture is heated and softened at a temperature equal to or higher than the melting point of the fatty acid ester.

By using a binder satisfying the above conditions as a binder mixed in the magnet powder, the amount of carbon and the amount of oxygen contained in the magnet can be reduced. Specifically, the amount of carbon remaining in the magnet after sintering is 2,000 ppm or less, more preferably 1,000 ppm or less. Moreover, the amount of oxygen remaining in the magnet after sintering is 5,000 ppm or less, more preferably 2,000 ppm or less.

Further, in order to increase the thickness precision of the molded body when molding the slurry or the composite which is heated and melted, the amount of the binder added is an amount which appropriately fills the space between the magnet particles. For example, the ratio of the binder to the total amount of the magnet powder and the binder is from 1 wt% to 40 wt%, more preferably from 2 wt% to 30 wt%, still more preferably from 3 wt% to 20 wt%.

[Method of manufacturing permanent magnet]

Next, a method of manufacturing the permanent magnet 1 of the present invention will be described with reference to Fig. 2 . Fig. 2 is an explanatory view showing a manufacturing procedure of the permanent magnet 1 of the embodiment.

First, Nd-Fe-B containing a specific fraction is produced (for example, Nd: 32.7 wt%, Fe (electricity) Iron (iron): 65.96 wt%, B: 1.34 wt%) ingot. Thereafter, the ingot is roughly pulverized to a size of about 200 μm by a masher, a crusher or the like. Alternatively, the ingot is melted, and a sheet is produced by strip casting, and coarsely pulverized by a hydrogen crushing method. Thereby, the coarsely pulverized magnet powder 10 is obtained.

Then, the coarsely pulverized magnet powder 10 is finely pulverized by a wet method using a bead mill 11 or a dry method using a jet mill. For example, in the fine pulverization using the wet method using the bead mill 11, the coarsely pulverized magnet powder 10 is finely pulverized into a specific range of particle diameter (for example, 0.1 μm to 5.0 μm) in a solvent, and the magnet powder is dispersed. In the solvent. Thereafter, the magnet powder contained in the solvent after the wet pulverization is dried by vacuum drying or the like to extract the dried magnet powder. Further, the type of the solvent to be pulverized is not particularly limited, and examples thereof include alcohols such as isopropyl alcohol, ethanol, and methanol, esters such as ethyl acetate, and lower hydrocarbons such as pentane and hexane, and benzene, toluene, and An aromatic group such as toluene, a ketone, a mixture of the above, and the like. Further, it is preferred to use a solvent which does not contain an oxygen atom in the solvent.

On the other hand, in the fine pulverization using a dry method using a jet mill, (a) an atmosphere containing an inert gas such as nitrogen, argon or helium in an oxygen content of substantially 0%, or (b) In an environment containing an inert gas such as nitrogen gas, argon gas or helium gas having an oxygen content of 0.0001 to 0.5%, the coarsely pulverized magnet powder is finely pulverized by a jet mill to form a particle diameter having a specific range (for example, 0.7). A fine powder having an average particle diameter of μm to 5.0 μm). In addition, when the oxygen concentration is substantially 0%, it is not limited to the case where the oxygen concentration is completely 0%, and it means that oxygen may be contained in an amount which is extremely small in the surface of the fine powder.

Then, the magnet powder finely pulverized by the bead mill 11 or the like is formed into a desired shape. Further, the formation of the magnet powder includes, for example, powder molding in which a mold is formed into a desired shape, or a green mold in which a mixture of the magnet powder and the binder is mixed into a desired shape. Further, the powder molding includes a dry method in which the dried fine powder is filled into the cavity, and a wet method in which the slurry containing the magnet powder is not dried and filled into the cavity. On the other hand, in the green molding, the mixture can be directly formed into the shape of the final product, and the mixture can also be made. Temporarily formed into a shape other than the shape of the final product, magnetic field alignment is performed, and then punching, cutting, deformation processing, and the like are performed, thereby forming a final product shape. In the following examples, the mixture was temporarily formed into a sheet shape (hereinafter referred to as a green sheet) and then processed into a final product shape. Further, in the case of forming the mixture into a sheet shape in particular, for example, it is formed by hot-melt coating in which a composite in which a mixture of a magnet powder and a binder is heated and formed into a sheet shape is formed. Or, a slurry containing a magnet powder, a binder, and an organic solvent is applied to a substrate to form a sheet-like slurry coating or the like.

Hereinafter, the green sheet molding using hot melt coating will be specifically described.

First, a powdery mixture (composite) 12 containing a magnet powder and a binder is prepared by mixing a binder in a magnet powder finely pulverized by a bead mill 11 or the like. Here, as the binder, a resin, a long-chain hydrocarbon, a fatty acid ester, a mixture of these, or the like can be used as described above. For example, it is preferred to use a thermoplastic resin containing a polymer having no oxygen atom and having depolymerization in the case of using a resin, and, on the other hand, a solid at room temperature in the case of using a long-chain hydrocarbon. And a long-chain saturated hydrocarbon (long-chain alkane) which is liquid above room temperature. Further, in the case of using a fatty acid ester, methyl stearate or methyl behenate or the like is preferably used. Further, the amount of the binder added is such that the ratio of the binder in the composite 12 added as described above to the total amount of the magnet powder and the binder is from 1% by weight to 40% by weight, more preferably from 2% by weight to 30% by weight. The amount of %, further preferably from 3 wt% to 20 wt%.

Further, in order to increase the degree of alignment in the subsequent magnetic field alignment step, an additive for promoting alignment may be added to the composite 12. As the additive for promoting the alignment, for example, a hydrocarbon-based additive can be used, and it is particularly preferable to use an additive having a polarity (specifically, an acid dissociation constant pKa of less than 41). Further, the amount of the additive to be added depends on the particle diameter of the magnet powder, and the smaller the particle diameter of the magnet powder, the more the amount of addition is required. The specific addition amount is 0.1 parts to 10 parts, more preferably 1 part to 8 parts, per part of the magnet powder. Further, the additive added to the magnet powder adheres to the surface of the magnet particles, and has an effect of assisting the rotation of the magnet particles in the magnetic field alignment treatment described below. As a result, the alignment is easy to advance when a magnetic field is applied. In the row, the direction of the easy magnetization axis of the magnet particles can be made to coincide with the same direction (ie, the alignment degree is improved). In particular, when a binder is added to the magnet powder, a binder is present on the surface of the particles, so that the frictional force at the time of alignment is improved, and the alignment property of the particles is lowered, so that the effect of adding an additive becomes more remarkable.

Further, the addition of the binder is carried out in an environment containing an inert gas such as nitrogen, argon or helium. Further, the mixing of the magnet powder and the binder is carried out, for example, by introducing the magnet powder and the binder into a mixer and stirring them with a stirrer. Further, in order to promote kneading, heating and stirring may be performed. Further, the mixing of the magnet powder and the binder is preferably carried out in an atmosphere containing an inert gas such as nitrogen, argon or helium. Further, in particular, when the magnet powder is pulverized by the wet method, the magnet powder may not be extracted from the solvent used for pulverization, and a binder may be added to the solvent and kneaded, and then the solvent may be volatilized. The following composite 12 was obtained.

Then, a green sheet is produced by forming the composite 12 into a sheet shape. In particular, in the hot melt coating, the composite 12 is melted and heated by heating the composite 12, and then applied to a support substrate 13 such as a separator. Thereafter, it is solidified by heat dissipation to form a long sheet-like green sheet 14 on the support substrate 13. Further, the temperature at which the composite 12 is heated and melted differs depending on the type or amount of the binder to be used, and is set to 50 to 300 °C. Among them, it must be set to a temperature higher than the melting point of the binder used. Further, in the case of using a slurry coating, the magnet powder and the binder (which may further contain an additive for promoting alignment) are dispersed in a large amount of an organic solvent, and the slurry is applied onto a support substrate 13 such as a separator. . Thereafter, the organic solvent is volatilized by drying to form a long sheet-like green sheet 14 on the support substrate 13.

Here, the coating method of the molten composite 12 is preferably a method in which the layer thickness controllability such as a slit die method or a calender roll method is excellent. In particular, in order to achieve a high thickness precision, it is preferable to use a mold method or a notch wheel coating which is excellent in layer thickness control property (i.e., a layer which can apply a high-precision thickness layer on the surface of a substrate). the way. example For example, in the slit die method, the composite 12 which is heated by the gear pump is extruded and inserted into a mold to perform coating. Further, in the calender roll method, a certain amount of the composite 12 is added to the gap between the two heated rolls, and the composite 12 which is thermally melted by the rolls is applied to the support substrate 13 while rotating the rolls. Further, as the support substrate 13, for example, a polyester film treated with polyfluorene oxide is used. Further, it is preferable to sufficiently perform the defoaming treatment so that air bubbles do not remain in the developed layer by using an antifoaming agent or heating vacuum defoaming. Further, it is also possible to adopt a configuration in which the melted composite 12 is formed into a sheet shape by extrusion molding or injection molding, and is extruded onto the support substrate 13 without being applied to the support substrate 13. The green sheet 14 is formed on the support substrate 13.

Hereinafter, the steps of forming the green sheet 14 by the slit mold method will be described in more detail with reference to Fig. 3 . Fig. 3 is a schematic view showing a step of forming a green sheet 14 by a slit mold method.

As shown in FIG. 3, the mold 15 used in the slit mold method is formed by overlapping the blocks 16 and 17, and the slit 18 and the cavity are formed by the gap between the blocks 16 and 17. (liquid storage unit) 19. The cavity 19 communicates with the supply port 20 provided in the block 17. Further, the supply port 20 is connected to a supply system of a coating liquid composed of a gear pump (not shown) or the like, and supplies the measured fluid-like composite 12 to the cavity 19 via the supply port 20 by a metering pump or the like. Further, the fluid-like composite 12 supplied to the cavity 19 is supplied with liquid to the slit 18, and is supplied at a constant amount per unit time and uniformly in the width direction, and is ejected from the slit 21 of the slit 18 in accordance with a predetermined coating width. ejection. On the other hand, the support base material 13 is continuously conveyed at a predetermined speed as the coating roller 22 rotates. As a result, the discharged fluid-like composite 12 is applied to the support substrate 13 with a specific thickness, and then heat-dissipated and solidified, whereby the elongated sheet-like green sheet 14 is formed on the support substrate 13. .

Further, in the step of forming the green sheet 14 by the slit mold method, it is preferable to actually measure the thickness of the sheet of the green sheet 14 after the application, and the gap between the mold 15 and the support substrate 13 based on the measured value. D performs feedback control. Further, it is preferable to supply the flow to the mold 15 The variation in the amount of the composite 12 is as small as possible (for example, the variation is ±0.1% or less), and the fluctuation in the coating speed is also reduced as much as possible (for example, the variation is suppressed by ±0.1% or less). Thereby, the thickness precision of the green sheet 14 can be further improved. Further, the thickness accuracy of the formed green sheet 14 is set to within ±10%, more preferably within ±3%, and even more preferably within ±1% with respect to the design value (for example, 1 mm). Further, on the other hand, in the calender roll method, by controlling the calendering conditions based on the measured values in the same manner, the transfer film thickness of the composite 12 on the support substrate 13 can be controlled.

Further, the thickness of the green sheet 14 is preferably set to be in the range of 0.05 mm to 20 mm. When the thickness is less than 0.05 mm, it is necessary to laminate a plurality of layers, so that productivity is lowered.

Then, the magnetic field alignment of the green sheet 14 formed on the support substrate 13 by the above-described hot melt coating is performed. Specifically, first, the green sheet 14 is softened by heating the green sheet 14 continuously conveyed together with the support base material 13. Specifically, the viscosity is softened until the green sheet 14 has a viscosity of 1 to 1500 Pa. s, more preferably 1~500Pa. s so far. Thereby, the magnetic field alignment can be appropriately performed.

Further, the temperature and time when the green sheet 14 is heated vary depending on the type or amount of the binder to be used, and is, for example, 100 to 250 ° C for 0.1 to 60 minutes. However, in order to soften the green sheet 14, it is necessary to set the temperature of the glass transition point or the melting point of the binder to be used. Further, as a heating method for heating the green sheet 14, there is, for example, a heating method using a hot plate or a heating method using a heat medium (polyoxygenated oil) as a heat source. Then, a magnetic field is applied to the in-plane direction and the longitudinal direction of the green sheet 14 which is softened by heating, thereby performing magnetic field alignment. The intensity of the applied magnetic field is set to 5000 [Oe] to 150,000 [Oe], preferably 10,000 [Oe] to 120,000 [Oe]. As a result, the C-axis (easy magnetization axis) of the magnet crystal contained in the green sheet 14 is aligned in one direction. Further, as a direction in which the magnetic field is applied, a magnetic field may be applied to the in-plane direction and the width direction of the green sheet 14. Further, it is also possible to adopt a configuration in which a plurality of green sheets 14 are simultaneously aligned with a magnetic field.

Further, when a magnetic field is applied to the green sheet 14, a step of applying a magnetic field simultaneously with the heating step may be employed, and a step of applying a magnetic field may be performed after the heating step and before the green sheet is solidified. Further, it is also possible to adopt a configuration in which the green sheet 14 coated by the hot melt coating is subjected to magnetic field alignment before solidification. In this case, no heating step is required.

Next, the heating step and the magnetic field alignment step of the green sheet 14 will be described in more detail using FIG. Fig. 4 is a schematic view showing a heating step and a magnetic field alignment step of the green sheet 14. Further, in the example shown in Fig. 4, an example in which the magnetic field alignment step is performed simultaneously with the heating step will be described.

As shown in Fig. 4, the heating and the magnetic field alignment of the green sheet 14 coated by the slit die method are performed on the long sheet-like green sheet 14 in a state of being continuously conveyed by a roller. That is, the apparatus for performing heating and magnetic field alignment is disposed on the downstream side of the coating device (such as a mold), and is carried out by a step that is continuous with the coating step.

Specifically, on the downstream side of the mold 15 or the application roller 22, the solenoid 25 is placed so that the conveyed support substrate 13 and the green sheet 14 pass through the solenoid 25. Further, the heating plate 26 is disposed in the solenoid 25 in the upper and lower sides of the green sheet 14 in pairs. Then, the green sheet 14 is heated by the heating plate 26 disposed in pairs up and down, and an electric current is supplied to the solenoid 25, thereby in the in-plane direction of the long sheet-like green sheet 14 (ie, with the green sheet) The sheet of 14 is parallel to the direction of the surface and a magnetic field is generated in the longitudinal direction. Thereby, the continuous conveyance of the green sheet 14 is softened by heating, and a magnetic field is applied to the in-plane direction of the softened green sheet 14 and the longitudinal direction (the direction of the arrow 27 in Fig. 4), whereby the green sheet 14 can be appropriately aligned uniformly. The magnetic field. In particular, by setting the direction in which the magnetic field is applied to the in-plane direction, the surface of the green sheet 14 can be prevented from fluffing.

Further, the heat dissipation and solidification of the green sheet 14 after the magnetic field alignment is preferably carried out in a conveyed state. Thereby, the manufacturing steps can be further streamlined.

In the case where the magnetic field is aligned in the in-plane direction and the width direction of the green sheet 14, a pair of magnetic field coils are disposed on the right and left sides of the conveyed green sheet 14 instead of the solenoid 25. Moreover, by applying current to each of the magnetic field coils, it is possible to grow in a long strip shape. A magnetic field is generated in the in-plane direction and the width direction of the sheet 14.

Further, the magnetic field alignment may be set to be perpendicular to the surface of the green sheet 14. In the case where the magnetic field is aligned in the direction perpendicular to the surface of the green sheet 14, it is performed by, for example, a magnetic field applying device using a magnetic pole piece or the like. Specifically, as shown in FIG. 5 , the magnetic field applying device 30 using a magnetic pole piece or the like includes two annular coil portions 31 and 32 that are arranged in parallel so that the central axis is the same axis, and are disposed in the coil portions 31 and 32, respectively. The two substantially cylindrical pole pieces 33 and 34 of the annular hole are arranged at a predetermined interval with respect to the conveyed green sheet 14. Then, by applying a current to the coil portions 31 and 32, a magnetic field is generated in a direction perpendicular to the surface of the green sheet 14, and the magnetic field alignment of the green sheet 14 is performed. Further, when the direction of the magnetic field alignment is set to be perpendicular to the surface of the green sheet 14, it is preferable that the green sheet 14 is also on the opposite side of the laminated support substrate 13 as shown in FIG. The laminated film 35. Thereby, the raising of the surface of the green sheet 14 can be prevented.

Further, instead of the heating method using the heating plate 26, a heating method using a heat medium (polyoxygenated oil) as a heat source may be used. Here, Fig. 6 is a view showing an example of a heating device 37 using a heat medium.

As shown in Fig. 6, the heating device 37 has a configuration in which a substantially U-shaped cavity 39 is formed inside the flat member 38 which is a heating element, and is heated to a specific temperature (for example, 100 to 300 ° C) in the cavity 39. It is used as a heat medium for the polyoxygen oil cycle. Further, in the solenoid 25, a heating device 37 is disposed in the upper and lower rows of the green sheet 14 in place of the heating plate 26 shown in Fig. 4 . Thereby, the continuously conveyed green sheet 14 is softened by the flat member 38 which generates heat by the heat medium. Further, the flat member 38 may be in contact with the green sheet 14, or may be disposed at a predetermined interval. Further, by applying a magnetic field to the in-plane direction and the longitudinal direction (the direction of the arrow 27 in FIG. 4) of the green sheet 14 by the solenoid 25 disposed around the softened green sheet 14, the green sheet 14 can be appropriately aligned. A uniform magnetic field. Further, in the heating device 37 using the heat medium shown in Fig. 6, the heating wire is not provided inside the heating plate 26 as usual, and therefore, even in the case of being placed in a magnetic field, there is no Lorentz force ( Lorentz force) After the wire is vibrated or cut, the heating of the green sheet 14 can be appropriately performed. Further, when the current is controlled, there is a problem that the heating wire is vibrated due to the ON or OFF of the power source, which causes fatigue fracture. However, by using the heating device 37 using the heat medium as the heat source, the problem can be eliminated. .

Here, in the case where the green sheet 14 is formed by a liquid material having a high fluidity such as a slurry by a conventional slit die method or a doctor blade method without using hot melt molding, if a magnetic field is generated When the green sheet 14 is moved in the gradient, the magnet powder contained in the green sheet 14 is pulled to the side where the magnetic field is strong, and the liquid phase of the slurry forming the green sheet 14, that is, the thickness deviation of the green sheet 14 is generated. On the other hand, when the composite 12 is formed into the green sheet 14 by hot melt forming as in the present invention, the viscosity at room temperature reaches tens of thousands to hundreds of thousands of Pa. s, the concentration of magnetic powder when the magnetic field gradient passes does not occur. Further, by carrying out the transportation and heating in a uniform magnetic field, the viscosity of the adhesive can be lowered, and the same C-axis alignment can be performed only with the torque in the uniform magnetic field.

In the case where the green sheet 14 is formed by a liquid material having a high fluidity such as a slurry containing an organic solvent, such as a conventional slit die method or a doctor blade method, the hot-melt molding is used. When the sheet having a thickness of more than 1 mm is foamed by the vaporization of the organic solvent contained in the slurry or the like during drying, it becomes a problem. Further, when the drying time is increased in order to suppress the foaming, precipitation of the magnet powder occurs, and a variation in the density distribution of the magnet powder with respect to the direction of gravity occurs, which causes the warpage after the firing. Therefore, in the molding of the slurry, in order to substantially regulate the upper limit of the thickness, it is necessary to form the green sheet to a thickness of 1 mm or less, and then laminate the green sheet. However, in this case, the binders are insufficiently fused to each other, and interlayer peeling occurs in the subsequent debonding step (calcining treatment), which becomes a decrease in the alignment of the C-axis (easy magnetization axis), that is, residual magnetic flux. The reason for the decrease in density (Br). On the other hand, when the composite 12 is formed into the green sheet 14 by hot melt forming as in the present invention, since the organic solvent is not contained, even when a sheet having a thickness of more than 1 mm is produced, it can be eliminated. The fear of foaming as described above. And the adhesive is fully integrated In this state, there is no entanglement of interlayer peeling in the debonding step.

Further, when a magnetic field is applied to the plurality of green sheets 14 at the same time, for example, continuous deposition is carried out in a state in which a plurality of sheets (for example, 6 sheets) of the green sheets 14 are laminated so that the green sheets 14 of the layers are placed on the solenoid 25 It is formed by means of internal passage. Thereby, productivity can be improved.

Thereafter, the green sheet 14 subjected to the magnetic field alignment is punched into a desired product shape (for example, a fan shape as shown in Fig. 1), and the formed body 40 is molded.

Then, by forming the formed body 40 at atmospheric pressure, or by pressure to a pressure higher than atmospheric pressure or a pressure lower than atmospheric pressure (for example, 1.0 Pa or 1.0 MPa) (especially in the present invention, a hydrogen atmosphere) Or in a mixed gas atmosphere of hydrogen and an inert gas, at a temperature at which the binder decomposes (in the case of adding an additive for promoting the alignment, a temperature which satisfies the conditions above the thermal decomposition temperature of the additive) for several hours to several tens The calcination treatment is carried out for an hour (for example, 5 hours). In the case of performing in a hydrogen atmosphere, for example, the supply amount of hydrogen in calcination is set to 5 L/min. By performing the calcination treatment, an organic compound such as a binder can be decomposed into monomers by a depolymerization reaction or the like and scattered and removed. That is, so-called decarburization which reduces the amount of carbon in the molded body 40 is performed. In addition, the calcination treatment is carried out under the conditions that the amount of carbon in the molded body 40 is 2,000 ppm or less, more preferably 1,000 ppm or less. Thereby, the entire permanent magnet 1 can be densely sintered by the subsequent sintering treatment without deteriorating the residual magnetic flux density or the coercive force. In the case where the pressurization condition at the time of the calcination treatment is carried out at a pressure higher than atmospheric pressure, it is preferably 15 MPa or less. Further, when the pressurization condition is set to a pressure higher than atmospheric pressure, more specifically 0.2 MPa, the effect of reducing the amount of carbon can be expected in particular.

Further, the binder decomposition temperature is determined based on the analysis results of the binder decomposition product and the decomposition residue. Specifically, a temperature range is selected in which the decomposition product of the binder is collected, no decomposition products other than the monomer are produced, and no side reaction due to the residual binder component is detected in the residue analysis. product. The decomposition temperature of the binder varies depending on the type of the binder, but it is set to 200 ° C to 900 ° C, more preferably 400 ° C. 600 ° C (for example 450 ° C).

Further, it is preferable that the calcination treatment slows down the temperature increase rate as compared with the case of sintering a normal magnet. Specifically, the temperature increase rate is set to 2 ° C / min or less (for example, 1.5 ° C / min). Therefore, in the case of performing the calcination treatment, as shown in FIG. 7, the temperature is raised at a specific temperature increase rate of 2 ° C/min or less, and after reaching a preset set temperature (adhesive decomposition temperature), the temperature is maintained at the set temperature. The calcination treatment is carried out for several hours to several tens of hours. The calcining treatment as described above removes the carbon in the formed body 40 stepwise rather than sharply by slowing down the rate of temperature rise, so that the density of the permanent magnet after sintering can be increased (i.e., reduced in the permanent magnet) Void). In addition, when the temperature increase rate is 2° C./min or less, the density of the permanent magnet after sintering can be made 95% or more, and high magnet characteristics can be expected.

Further, the molded body 40 obtained by calcining by calcination may be further subjected to a dehydrogenation treatment while maintaining the vacuum atmosphere. In the dehydrogenation treatment, NdH ₃ (large activity) in the molded body 40 produced by the calcination treatment is changed stepwise from NdH ₃ (large activity) to NdH ₂ (small activity). The activity of the molded body 40 activated by the calcination treatment is lowered. Thereby, even when the molded body 40 calcined by the calcination treatment is moved to the atmosphere, Nd can be prevented from being combined with oxygen, and the residual magnetic flux density or coercive force is not lowered. Further, an effect of restoring the structure of the magnet crystal from NdH ₂ or the like to the Nd ₂ Fe ₁₄ B structure can be expected.

Then, a non-pressure sintering treatment for non-pressure-sintering the formed body 40 which has been calcined by calcination is performed. Specifically, the molded body 40 is not pressurized, but is heated to a firing temperature of about 800 ° C to 1080 ° C at a specific temperature increase rate in a vacuum atmosphere, and is maintained for about 0.1 to 2 hours. In this period, vacuum firing is performed, and as the degree of vacuum, it is preferably 5 Pa or less, preferably 10 ^-2 Pa or less. Then, sintering is performed, and as a result, a molded body of the sintered magnet (hereinafter referred to as sintered body 50) is obtained.

Then, a pressure sintering treatment is performed on the sintered body 50 which is sintered by non-compression sintering and further subjected to pressure sintering. Furthermore, the pressing direction at the time of pressure sintering is set as opposed to the application The direction of the magnetic field (for example, the in-plane direction and the length direction of the green sheet) is perpendicular to the direction. That is, the direction perpendicular to the C-axis (easy magnetization axis) direction of the magnet particles aligned by the magnetic field alignment treatment is applied. Examples of the pressure sintering include hot press sintering, hot pressurization (HIP) sintering, ultrahigh pressure synthetic sintering, gas pressure sintering, and discharge plasma (SPS) sintering. In order to suppress the grain growth of the magnet particles during sintering and to suppress the warpage caused by the magnet after sintering, it is preferably used for uniaxial pressure sintering in a uniaxial direction and by electric conduction sintering. Sintered SPS is sintered. Further, in the case of sintering by SPS sintering, it is preferred to set the pressurization value to, for example, 0.01 MPa to 100 MPa, and to increase the temperature to 10 ° C/min to 940 ° C in a vacuum atmosphere of several Pa or less, and thereafter to maintain 5 minute. Thereafter, the mixture was cooled, and heat treatment was again performed at 300 ° C to 1000 ° C for 2 hours. Then, sintering is performed, and as a result, permanent magnet 1 is produced. In the present invention, by performing the above-described pressure sintering, the density of the permanent magnet can be increased before the pressure sintering (that is, the void in the permanent magnet is reduced). In particular, when the density of the permanent magnet after sintering is 95% or more, a high magnet characteristic can be expected. In addition, by setting the temperature increase rate in the calcining treatment to 2 ° C / min or less as described above, the permanent magnet of the degree of sintering can be further increased in density.

Hereinafter, the pressure sintering step of the sintered body 50 by SPS sintering will be described in more detail with reference to Fig. 8 . Fig. 8 is a schematic view showing a pressure sintering step of the sintered body 50 by SPS sintering.

In the case where SPS sintering is performed as shown in Fig. 8, first, a sintered body 50 is provided in a graphite sintered mold 41. Further, the sintered body 50 is provided so as to be pressurized in a direction perpendicular to a direction in which a magnetic field is applied (for example, an in-plane direction and a longitudinal direction of the green sheet). Then, the sintered body 50 provided in the sintering mold 41 is held in the vacuum chamber 42, and the upper punch 43 and the lower punch 44, which are also made of graphite, are provided. Then, a low voltage and high current DC pulse voltage/current is applied using the punch electrode 45 connected to the upper portion of the upper punch 43 and the punch electrode 46 connected to the lower portion of the lower punch 44. At the same time, a load is applied to the upper punch 43 and the lower punch 44 from the vertical direction by a pressurizing mechanism (not shown). the result, The sintered body 50 provided in the sintering mold 41 is pressed while being pressed. Further, in order to improve productivity, it is preferred to simultaneously perform SPS sintering on a plurality of (for example, ten) shaped bodies. Further, when a plurality of sintered bodies 50 are simultaneously subjected to SPS sintering, a plurality of sintered bodies 50 may be disposed in one space, and each sintered body 50 may be disposed in a different space. Further, when each sintered body 50 is disposed in a different space, the sintered body 50 is pressurized in each space, and the upper punch 43 or the lower punch 44 is integrated between the spaces ( In other words, the upper punch 43 and the lower punch 44 which are integrally driven can be configured to simultaneously press a plurality of molded bodies in the respective spaces.

[Examples]

Hereinafter, an embodiment of the present invention will be described in comparison with a comparative example.

(Example 1)

Example 1 was a Nd-Fe-B based magnet, and the alloy composition was set to Nd/Fe/B = 32.7 / 65.96 / 1.34 in wt%. Further, a composite is produced by adding a binder to the magnet powder. As the binder, polyisobutylene (PIB) is used. Further, the amount of the binder added to the magnet powder was set to 4 parts. Further, the heat-melted composite was applied to a substrate by a slit die method to form a green sheet having a thickness of 8 mm. Further, the formed green sheet was heated by a heating plate heated to 200 ° C for 5 minutes, and a magnetic field of 12 T was applied to the green sheet in the in-plane direction and the longitudinal direction to thereby perform magnetic field alignment. Then, after the magnetic field is aligned, the green sheet which has been punched into a desired shape in a hydrogen atmosphere is calcined (heating rate is 1.5 ° C / min and maintained at 450 ° C for 5 hours), and thereafter, vacuum sintering is performed. Pressure sintering. Further, the sintered body obtained by sintering by non-pressure sintering was placed in a sintering mold of an SPS sintering apparatus, and pressed in a direction perpendicular to the direction in which the magnetic field was applied by 10 kgf/cm ² and held at 920 ° C for 5 minutes. Pressure sintering is performed. In addition, the other steps are the same as the above [manufacturing method of permanent magnet].

(Examples 2 and 3)

Each was produced under the same conditions as in Example 1.

(Comparative examples 1 to 3)

Each of the permanent magnets of Examples 1 to 3 was subjected to pressure sintering, and only the permanent magnet which sintered the molded body by non-pressure sintering (that is, before the permanent magnets of Examples 1 to 3 were subjected to pressure sintering) Permanent magnet).

(Comparative Example vs. Comparative Example)

The degree of alignment [%] and density [%] of each of the sintered magnets of Examples 1 to 3 and Comparative Examples 1 to 3 were measured. Further, the residual magnetic flux density [kG] and the coercive force [kOe] were measured for each of the magnets of Examples 1 to 3 and Comparative Examples 1 to 3. In addition, the measurement of the degree of alignment is performed by using a DC self-recording magnetic fluxmeter ("TRF-5BH-25auto" manufactured by Dongying Industrial Co., Ltd., the maximum applied magnetic field of 25 kOe) versus Br (residual magnetic flux density) and Jmax (maximum Magnetization) was carried out by measuring and calculating Br/Jmax. A list of measurement results is shown in FIG.

When the permanent magnet of Example 1 was compared with the density of the permanent magnet of Comparative Example 1, the density of the permanent magnet of Comparative Example 1 which was not subjected to pressure sintering was 97%, and thereafter, pressure sintering was performed. The permanent magnet of Example 1 had a higher density than the permanent magnet of Comparative Example 1, and had a density of 99%. That is, it is considered that the density of the magnet is improved by the pressure sintering after the non-pressure sintering. Further, as shown in Fig. 9, the density of the permanent magnet has a large influence on the characteristics of the magnet, and the permanent magnet of the first embodiment having a high density shows a high value in terms of residual magnetic flux density or coercive force. In addition, it was confirmed that sufficient magnetic properties can be exhibited if the density is 95% or more. Further, even after the temporary non-pressure sintering and the density of the permanent magnet before the pressure sintering is less than 95%, the density can be made 95% or more by pressure sintering.

Further, when the permanent magnet of the first embodiment is compared with the degree of alignment of the permanent magnet of Comparative Example 1, the degree of alignment of the permanent magnet after the pressure sintering (Example 1) and the permanent magnet before the pressure sintering are performed ( In Comparative Example 1), the degree of alignment was not lowered. That is, it can be seen that the direction of pressurization when performing pressure sintering is the direction in which the magnetic field is applied (by magnetic field alignment) The vertical direction of the C-axis (easy magnetization axis) direction of the magnet particles to be aligned is not changed in the direction of the C-axis (easy magnetization axis) of the magnet particles after the magnetic field alignment of the sintered body is pressed. Maintain a high alignment state.

Further, in the same manner as in Examples 2 and 3, the density was improved and the magnet characteristics were improved as compared with Comparative Examples 2 and 3. Also, the degree of alignment has not decreased.

As described above, in the method for producing the permanent magnet 1 and the permanent magnet 1 of the present embodiment, the magnet raw material is pulverized into a magnet powder, and the pulverized magnet powder and the binder are mixed to produce the composite 12. Then, the resulting composite 12 is formed into a sheet shape on the support substrate 13 by hot melt molding to produce a green sheet 14. Thereafter, the formed green sheet 14 is heated and softened, and a magnetic field is applied to the heated green sheet 14, thereby performing magnetic field alignment, and further, vacuum sintering of the green sheet 14 after the magnetic field is aligned is performed. Permanent magnet 1 is produced by pressure sintering. As a result, the shrinkage due to sintering becomes uniform, and deformation such as warpage or depression after sintering does not occur, and the pressure is not uniform when there is no pressurization, so that it is not necessary to perform the correction processing after the previous sintering. Simplify manufacturing steps. Thereby, the permanent magnet can be formed with higher dimensional accuracy. Moreover, even when the permanent magnet is thinned, the material yield can be prevented from decreasing and the number of processing steps can be prevented from increasing. Further, since the formed green sheet 14 is heated and a magnetic field is applied to the heated green sheet 14 to perform magnetic field alignment, the green sheet can be appropriately aligned with the green sheet 14 after the molding, and the permanent magnet can be improved. Magnetic properties. Further, when there is no magnetic field alignment, the liquid phase is generated, that is, the thickness deviation of the green sheet 14 is exceeded. Further, by carrying out the transportation and heating in a uniform magnetic field, the viscosity of the adhesive can be lowered, and the same C-axis alignment can be performed only with the torque in the uniform magnetic field. Further, even in the case of producing the green sheet 14 having a thickness of more than 1 mm, the foaming agent does not foam and the binder is sufficiently fused, so that no delamination occurs in the debonding step (calcining treatment). Further, since the molded body 40 is sintered by non-pressure sintering and then sintered by pressure sintering, the density of the permanent magnet after sintering can be made high density (all densification). Moreover, when performing pressure sintering, it is perpendicular to the direction of the applied magnetic field. Since the sintered body 50 is pressurized, the direction of the C-axis (easy magnetization axis) of the aligned magnet particles is not changed by the pressurization of the sintered body 50. Therefore, it is possible to prevent a decrease in magnetic properties without lowering the alignment degree.

Further, in the step of sintering the sintered body 50 by pressure sintering, sintering is performed by uniaxial pressure sintering, so that shrinkage due to sintering becomes uniform, and warpage or depression after sintering can be prevented. Deformation. Moreover, it is also possible to prevent a decrease in the degree of alignment.

Further, in the step of sintering the sintered body 50 by pressure sintering, sintering is performed by electric conduction sintering, so that the temperature can be rapidly increased and cooled, and sintering can be performed in a lower temperature region. As a result, the temperature rise and the holding time in the sintering step can be shortened, and a dense sintered body which suppresses grain growth of the magnet particles can be produced.

Moreover, by setting the density of the rare earth permanent magnet to 95% or more, it is possible to prevent the magnetic properties from being greatly lowered by the voids without forming voids inside the magnet.

Moreover, even when the molded body 40 is subjected to calcination treatment for decarburization, the density of the permanent magnet after sintering can be increased.

Further, the molded body 40 is heated to a set temperature at a temperature increase rate of 2 ° C/min or less in a non-oxidizing atmosphere, and then held at a set temperature for a predetermined period of time to perform a calcination treatment, so that it can be accompanied by a slow temperature. The carbon contained in the formed body 40 is removed stepwise. Therefore, a rare earth permanent magnet having a high density can be produced without forming a large number of voids inside the magnet.

Further, since the magnet obtained by sintering the green sheet formed by mixing the magnet powder and the binder constitutes a permanent magnet, the shrinkage due to sintering becomes uniform, and deformation such as warpage or depression after sintering does not occur. Further, since the pressure is not uniform when there is no pressurization, it is not necessary to perform the correction processing after the previous sintering, and the manufacturing steps can be simplified. Thereby, the permanent magnet can be formed with higher dimensional accuracy.

It is a matter of course that the present invention is not limited to the above-described embodiments, and various modifications and changes can be made without departing from the spirit and scope of the invention.

For example, the pulverization conditions, the kneading conditions, the molding conditions, the magnetic field alignment step, the calcination conditions, the sintering conditions, and the like of the magnet powder are not limited to the conditions described in the above examples. For example, in the above embodiment, the magnet raw material is pulverized by wet pulverization using a bead mill, or may be pulverized by dry pulverization using a jet mill. Moreover, if the environment in the case of calcination is a non-oxidizing environment, it may be carried out in an environment other than a hydrogen atmosphere (for example, a nitrogen atmosphere, a helium atmosphere, or the like, an argon atmosphere, or the like). Further, in the above embodiment, the magnet is sintered by SPS sintering, and the magnet may be sintered by another pressure sintering method (for example, hot press sintering). Further, the calcination treatment may be omitted. In this case, decarburization is carried out during the sintering process.

Further, in the above examples, a resin, a long-chain hydrocarbon or a fatty acid ester is used as the binder, and other materials may be used.

Further, the permanent magnet can be produced by calcining and sintering a molded body formed by molding (for example, powder molding) other than green sheet molding. In this case, it is also expected to increase the density by pressure sintering. Further, in the above embodiment, after the magnet powder is molded, calcination is carried out in a hydrogen atmosphere or a mixed gas atmosphere of hydrogen gas and an inert gas, and the magnet powder before molding may be calcined to be used as a calcined body. The magnet powder is formed into a molded body, followed by sintering, thereby producing a permanent magnet. According to this configuration, since the powdery magnet particles are calcined, the surface area of the magnet to be calcined can be expanded as compared with the case where the magnet particles after molding are calcined. That is, the amount of carbon in the calcined body can be more surely reduced. In the case where the green body is formed, in order to thermally decompose the binder by the calcination treatment, it is preferred to carry out the calcination treatment after the molding.

Further, in the above embodiment, the heating step and the magnetic field alignment step of the green sheet 14 are simultaneously performed, and the magnetic field alignment step may be performed after the heating step and before the green sheet 14 is solidified. Further, when the green sheet 14 to be applied is solidified (that is, the green sheet 14 is softened even if the heating step is not performed), the heating step may be omitted.

Moreover, in the above embodiment, the slit is performed by one consecutive series of steps The coating step, the heating step, and the magnetic field alignment step of the mold method may also be configured not by continuous steps. Further, it may be divided into a first step before the coating step and a second step after the heating step, and each step is carried out. In this case, the green sheet 14 to be applied may be cut to a specific length, and the green sheet 14 in a stationary state may be heated and magnetic field applied to perform magnetic field alignment.

Further, in the present invention, an Nd-Fe-B-based magnet is exemplified, and other magnets (for example, lanthanum-cobalt magnet, alnico magnet, ferrite magnet, or the like) may be used. Further, in the alloy composition of the magnet, in the present invention, the Nd component is made more than the metered composition, and may be a metering composition.

1‧‧‧ permanent magnet

10‧‧‧ coarsely crushed magnet powder

11‧‧‧jet mill

12‧‧‧Complex

13‧‧‧Support substrate

14‧‧‧Life

15‧‧‧Mold

25‧‧‧ Solenoid

40‧‧‧Formed body

50‧‧‧Sintered body

Claims (16)

A rare earth permanent magnet characterized by the steps of: pulverizing a magnet raw material into a magnet powder; forming a shaped body by molding the pulverized magnet powder; and applying the shaped body a step of performing a magnetic field alignment by a magnetic field; a step of sintering the formed body aligned by a magnetic field by non-pressure sintering; and a pressure sintering by pressurizing in a direction perpendicular to a direction in which the magnetic field is applied The step of sintering the sintered body, which is the above-mentioned molded body which is sintered by non-pressure sintering, is further sintered. The rare earth permanent magnet of claim 1, wherein the sintering is performed by uniaxial pressure sintering in the step of sintering the sintered body by pressure sintering. The rare earth permanent magnet of claim 1, wherein in the step of sintering the sintered body by pressure sintering, sintering is performed by electric conduction sintering. The rare earth permanent magnet of claim 1, wherein the rare earth permanent magnet obtained by sintering by pressure sintering has a density of 95% or more. The rare earth permanent magnet of claim 1, wherein the formed body is calcined in a non-oxidizing atmosphere before the non-pressure sintering of the formed body, thereby removing carbon in the formed body. The rare earth permanent magnet according to claim 5, wherein in the step of calcining the formed body, the formed body is heated to a set temperature at a temperature increase rate of 2 ° C/min or less in a non-oxidizing atmosphere, and then Keep it at a set temperature for a certain period of time. The rare earth permanent magnet according to any one of claims 1 to 6, wherein in the step of forming the magnet powder into a shaped body, a mixture of the magnet powder and the binder is mixed. A green sheet as the above-mentioned molded body was produced by molding the above mixture into a sheet shape. The rare earth permanent magnet according to any one of claims 1 to 6, wherein in the step of molding the magnet powder into a molded body, the magnet powder is formed into the molded body by powder molding. A method for producing a rare earth permanent magnet, comprising: a step of pulverizing a magnet raw material into a magnet powder; a step of forming a shaped body by molding the pulverized magnet powder; and applying a magnetic field to the formed body a step of performing magnetic field alignment; a step of sintering the above-mentioned formed body aligned by a magnetic field by non-pressurization sintering; and a pressure sintering by pressurization in a direction perpendicular to a direction in which a magnetic field is applied, by the above-mentioned non- The step of sintering the sintered body, which is a sintered body, which is sintered by pressure sintering. The method for producing a rare earth permanent magnet according to claim 9, wherein in the step of sintering the sintered body by pressure sintering, sintering is performed by uniaxial pressure sintering. The method for producing a rare earth permanent magnet according to claim 9, wherein in the step of sintering the sintered body by pressure sintering, sintering is performed by electric conduction sintering. The method for producing a rare earth permanent magnet according to claim 9, wherein the density of the rare earth permanent magnet obtained by sintering by pressure sintering is 95% or more. The method for producing a rare earth permanent magnet according to claim 9, wherein the molded body is calcined in a non-oxidizing atmosphere before the non-pressure sintering of the formed body, thereby removing carbon in the molded body. The method for producing a rare earth permanent magnet according to claim 13, wherein in the step of calcining the shaped body, the formed body is subjected to a non-oxidizing environment. After the temperature increase rate of 2 ° C/min or less is raised to the set temperature, the temperature is maintained at the set temperature for a certain period of time. The method for producing a rare earth permanent magnet according to any one of claims 9 to 14, wherein in the step of forming the magnet powder into a shaped body, a mixture of the magnet powder and the binder is mixed by using the mixture. The green sheet as the molded body was produced into a sheet shape. The method for producing a rare earth permanent magnet according to any one of claims 9 to 14, wherein in the step of molding the magnet powder into a molded body, the magnet powder is formed into the molded body by powder molding.